Funds are requested for the purchase of a Thermo LTQ-Orbitrap Elite mass spectrometer with electron transfer dissociation (ETD) capability. The requested instrument will be installed at, and managed by the W. M. Keck Proteomics Facility at the University of California Riverside. There are a core group of 14 NIH-funded investigators at UC Riverside who require extensive access to the proposed LTQ-Orbitrap Elite system for proteomic analysis. The progress of these research projects is currently hampered by the lack of a high- performance LC-MS/MS system for global proteome quantification, large-scale mapping of post-translational modifications, protein complex, and protein conformation studies. The availability of the proposed instrument will have an immediate and positive impact on the progress of these research projects. In particular, the high scan rate of the linear ion trap, together with the high mass-resolving power and high mass accuracy of the Orbitrap mass analyzer, provides capability in identifying and quantifying a large number of proteins with high confidence. In addition, the availability of electron transfer dissociation as an ion dissociation technique on the proposed instrument facilitates the unambiguous identifications of post-translational modifications with great accuracy. The availability of this state-of-the-art proteomis platform will further promote biomedical research at UC Riverside and enhance the research experience of students and post-docs from under-represented minority groups.